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In this paper, we report on abundant fossils of Platybelodon from the Middle Miocene of the Linxia Basin, China. Most of the fossils were discovered at two localities (Laogou and Zengjia) in the upper Middle Miocene Hujialiang Formation, and possess derived characters for the genus, including a relatively slender upper incisor, the development of a transverse ledge on the narrowest part of the mandibular symphysis, narrow, elongate and hypsodont third molars, the development of fourth loph(id)s on the second molars, and the development of small enamel conules and cementum in the interloph(id)s. Following comparisons with other Eurasian platybelodonts, we assign these remains to Platybelodon grangeri, and demonstrate that they are morphologically intermediate between P. grangeri from the Tunggurian localities of Tarim Nor and Platybelodon Quarry in Inner Mongolia. We suggest that the locality of Laogou may be younger than that of Zengjia, based on the occurrence of platybelodonts showing a suite of more derived characters. In addition, we assign two further specimens of Platybelodon from the lower Middle Miocene Dongxiang Formation of the Linxia Basin to Platybelodon danovi, owing to their retention of plesiomorphic characters distinguishing them from other Linxia Platybelodon fossils. Based on a cladistic analysis, we propose an evolutionary sequence of platybelodonts in Eurasia, and discuss potential functional adaptations.
Finely−bedded lacustrine deposits of the Aptian (Lower Cretaceous) Xiagou Formation exposed in the Changma Basin of Gansu Province, northwestern China, have yielded numerous fossil vertebrate remains, including approximately 100 avian specimens. Though the majority of these birds appear referable to the ornithuromorph Gansus yumenensis, a number of enantiornithine fossils have also been recovered. Here we report on a specimen consisting of a complete, three−dimensionally preserved sternum, furcula, and sternal ribs that represents a second ornithuromorph taxon from the Xiagou Formation at Changma. The fossil exhibits morphologies that distinguish it from all previously−known Xiagou birds and demonstrate that it represents a derived non−ornithurine member of Ornithuromorpha. Though it is morphologically distinct from the equivalent elements of all other described ornithuromorphs, the material is too incomplete to justify the erection of a new taxon. Nonetheless, it increases the taxonomic diversity of the Xiagou avifauna, thereby expanding our knowledge of Early Cretaceous avian diversity and evolution.
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The distant evolutionary ancestry of mammals is documented by a rich therapsid fossil record. While sphenacodontid synapsids are considered the sister−group of therapsids, the place of origin of therapsids is an enigma, largely because of a long standing morphological and temporal gap (Olson’s Gap) in their fossil record. We describe a new large predatory synapsid, Raranimus dashankouensis gen. et sp. nov., from the Middle Permian of Dashankou in China which has a unique combination of therapsid and sphenacodontid features. This specimen is of great significance asit is a basal therapsid which is the sister taxon to all other therapsids. The fact that it was found in association with Early Permian tetrapods (Anakamacops and Belebey) suggests that it is the oldest therapsid and provides the first evidence of therapsid−bearing rocks which cover Olson’s Gap. It further supports that therapsids may have had a Laurasian rather than Gondwanan origin.
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